Hi,

I'm trying to understand these queries. They both gather data from
the wait event views, but they return totally different results. The
one that comes from the system views seems to be much more static.
Should I be looking at one over the other, or is one more accurate on
the system health?

SELECT a.event, a.total_waits, a.time_waited, a.average_wait
FROM v$system_event a, v$event_name b, v$system_wait_class c
WHERE a.event_id=b.event_id
AND b.wait_class#=c.wait_class#
AND c.wait_class IN ('Application','Concurrency')
ORDER BY average_wait DESC;

SELECT event, total_waits, time_waited, average_wait
FROM (SELECT a.event, a.total_waits, a.time_waited, a.average_wait,
ROW_NUMBER() OVER (PARTITION BY a.event ORDER BY average_wait DESC)
rnum
FROM v$session_event a, v$event_name b, v$session_wait_class
c
WHERE a.event_id=b.event_id
AND b.wait_class#=c.wait_class#
AND c.wait_class IN ('Application','Concurrency'))
WHERE rnum = 1
ORDER BY average_wait DESC;

On Jun 22, 11:44*am, The Magnet <a... (AT) unsu (DOT) com> wrote:
The view v$session_event will contain information about current
sessions only. On a busy system new sessions are being created all
the time and others exit ceasing to exist. Session information is
rolled up into the system statistics which would go back to instance
startup.

HTH -- Mark D Powell --